An elastic rotary actuator of the above-defined type is known from EP2239479. This known actuator offers evident advantages, such as in particular the fact that it is compact, it has a modular structure which allows to use it even within complex robotic systems and it allows to actively adjust the stiffness in a wide interval of desired stiffness values. On the other hand, this known actuator suffers from the drawback that the output member is subject, due to the provision of elastic means interposed between itself and the input member, to oscillations about the desired position. In certain applications these oscillations may not be tolerated, since for instance the output member may be required to reach the desired position without going beyond it.